System and method of determining distance



June 21,, 1938. BAlLEY 2,120,971

r SYSTEM AND METHOD OF DETERMINING DiSTANCE Filed Dec. "21, 1935 ssheets-sheet 1 N m 3 Q g 3 L5 I. n l illllllm-l- & A 5 i FIG. I

INVENTOk y AREA/LE) I A LQRNE Y June 21, 1938. A. B. BAILEY 2,120,971

SYSTEM AND METHOD OF DETERMINING DISTANCE Filed Dec. 21, 1935 5Sheets-Sheet 2 INVENTOR A .8. BAILEY ATTORNEY q d 3 m! on Q T I 3 Q on2. b 2 Q T m 3 a @i W E T m k 1i 8% 3 M ELL d on N Rfi fi P WH T h Mk han m \%Q@ R k Qb Q N Pk E June 21, 1938. A. B. BAILEY 2,120,971

SYSTEM AND METHOD OF DETERMINING DISTANCE I Filed Dec. 21, 1935 3 sheetssheet 3 A TTOBNE v -A.8. BAILEY BY Patented June 21, 138

SYSTEM AND METHOD OF DETERIVIINING DISTANCE Arnold B. Bailey, New York,N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York,N. Y., a corporation of New York Application December 21, 1935, SerialNo. 55,569

15 Claims. (c1. 117-352) lines covering short distances in the UnitedStates arelatively few years ago, commercial transcontinental air routesnow span the country from New York to Los Angeles and from New Orleansto Chicago. Remarkable as this progress has been, the potentiality andfuture utilization of the airplane in transportation is stupendous. onemost important factor responsible for the advance in air transportationin recent years is the development of sundry means for rendering airtransportation less hazardous. While at present the'hazard oftransportation by air is considerably less than that of a few years ago,airplane disasters occur far too frequently. The landing of an airplanein foggy weather or when visibility is poor is perhaps one of thegreatest contributory causes of airplane disasters. For safe landingwhen blind flying, a quick, accurate indication of the height of anairplane above ground, particularly at .low altitudes, is highlyessential.

In accordance with this invention,- an indication of the height of anairplane above ground is obtained by means. of transmission andreception after reflection of a sonic or supersonic wave. A supersonicor'sonic wave is transmitted at predetermined intervals. The wave, afterreflection from the ground, indicates by means of one or several of aplurality of gaseous discharge device the height of the airplane aboveground.

Ina specific embodiment, a pulse of current employedto emit thewave-also charges a confrom the source to the ground or other reflectingsurface and returns to the source, the illumina tion of one of theplurality of devices indicates the particular height of the airplane orother mobile object above the reflecting surface. Alternately, the pulseemployed to transmit the wave causes a condenser to commence to chargeso that the potential built up across the condenser increases with time.,The wave after reflection actuates the discharge of the condenserthrough a plurality of gaseous space discharge devices. The gaseousspace discharge devices are biased so that they flash at varyingmagnitudes of the electromotive force resulting from the discharge ofthe condenser. Since the magnitude varies with the charging time or theinterval required for the wave to travel to ground and return, thenumber of devices ignited indicates the distance.

A more comprehensive understanding of this invention is obtained byreference to the accompanying drawings in which:

Fig. 1 is a schematic diagram of this invent on in which distance isindicated by the illumination of onset a plurality of discharge devices;

Fig. 2 shows an embodiment of this invention in which altitude isascertained by the illumination of one or more of a plurality ofdischarge devices;

Fig. 8 is a schematic diagram in which the distance is indicated indigits of a particular unit of .measurement; and

Figs. 1A and 2A showthe indicating devices employed in the system shownin Figs. 1 and 2, respectively, while Figs. 3Aand 3B illustrate theindicating device used on the system shown in Fig. 3. I

In the system shown in Fig. 1, a particular altitude or distance isindicated by the illumination of one of a plurality of dischargedevices. The system is capable of indicatinga particular distance withintwo ranges of distances. A motor I rotates a shaft 4 at a uniform speedby means of sets of gears 2 and}. Fixedly attached to the shaft 4 is acam 5 with an elevation on the periphery thereof. The elevation on theperiphery of the wheel 5 controls a pair of contacts 6 to energize a.relay l0 through a contact 1 and an armature v8 of 'a relay 9 from asource of current l2 of the relay lfl results in the keying of theoutput of an inductor-alternator l3 to transmit a sonic or supersonicwave ortrain of waves from a transmitter Id. The inductor-alternator I3is of the type described inan article entitled, Inductor-alternators forSignaling Purposes by F. Merrill in Electrical Engineering, January1934, Vol. 53, No. 1, pages 78 to 86 and is prefer- -ably capable ofproducing oscillations of 1000 a II. The engagement of a contact andarmature cycles. .Any other type of oscillator. however,

- may be employed instead of the inductor-alternator l3. The transmitterI4 is preferably of the.

" mitter' I 4 it is reflected upon the terrain or sea directional typeand is located for the determination of altitude on the underside of anairplane.

The elevation on the periphery of the wheel 5 is constructed so that fora brief interval once-during each revolution of the shaft 4, the contact6 engages to transmit a waveor train of waves from the transmitter l4.The energization of relay III also results in the momentary charging vof a condenser i'i fromthe source of current II through a resistance l6and an armature and make .contact id of relay l0. After thewave or trainof waves is transmitted from the transbottom and is impressed upon amicrophone l8 located in close proximity to the transmitter l4. If thesystem is employed on an airplane, the microphone is located on theunderside of the airplane in closeproxim'ity of the transmitter l4.

; The impressed waves are amplified by an amplifler to energize a relayI9. The amplifier is indicated by a labeled block diagram in thedrawings. Fixedly attached to the shaft 4 is a brush 2|..

, The brush is in enga'geable relation with a slip ring and a, pluralityof commutator segments 22 to connect the slip ring with one. of theplurality of segments 22. Each of' the commutator segments "22, numberedconsecutivelyiA to IDA,

' is of'equal arcuate length. The brush 2| always simultaneously withthe engagement of the con- 'tential.

'of relay l9 through tacts 6 is not discharged.

Each of the, plurality of commutator-segments is connected to oneelectrode of a separate dielectrode luminous discharge device filledwith neon gas. The other electrode of each device 23' is connectedthrough a protective resistance 26 to one terminal of a source. ofcurrent 21. The

other terminal of the source 21 is at ground po- The electrode of eachdevice 23 connected to its respectively associated segment isconnected-through a resistance 28 to ground.

The slip ring Mi is connected to the make contact a copper oxiderectifier 29 and a break contact 30 and armature 3| of relay 9. Thearmature of relay i9 is connected to the other plate of condenser Ibeing connected to ground. When a wave. or train of waves afterreflection on the terrain is impressed upon the microphone l8 therectified current in the output of the amplifier energizes relay l9 tocomplete a engagement of its armature and make contactcircuit by thefrom ground through condenser H, the armature and make contact of relayl9, armature 3|, contact 30, copper oxide rectifier 29, slip ring 20,

brush 2|, one of the plurality of segments ,22. the respectivelyassociated illuminating device 23 of the segment 22 with which the brushis in contact, resistance 26, source 21 to ground. The

condenser I1 is accordingly discharged-and its potential applied to the.particular illuminating device associated with the segment 22 upon whichthe brush 2| is at that time engaged. The characteristic of illuminatingdevices 23 is such and the value of the source 21 is selected so thatunder static conditions with no transient voltage across the resistance28 the device 23 does not the time required for the shaft 22 arenumbered -.discharge. I When the surge resulting from the discharge ofthe condenser I1 is impressed upon a particular device 23, however, thepotential across the device increases above its critical discharge valueand the device becomes illuminated. Whenthe surge ceases, the device 23continues .to be illuminated since the circuit values are selected so.that it maintains the discharge with a lower potential than that whichis, necessary for initial discharge. The circuit for maintaining thedischarge after the initial ignition of the device 23 is from ground,resistance 28, device 23, resistance 26, source 21 to ground. Q

A'scavenger brush 32 fixedly attached to the shaft'l is in engageable'relation with'the plurality of commutator segments 22 and is separatedfrom the brush 2| the arcuate length of one segment 22. The brush 32 isalso in contact with a slip ring 33 connected to one electrode of eachof theplurality of illuminating devices 23 through to each other throughresistance 26 to shunt the source 21. The shunting of the source 2'!results in the de-ignition of the device 23.

The above-described system indicates a. particular distance within apredetermined range. A longitudinal wave or train of waves istransmitted by the transmitter M as a result of the engagement ofcontacts 6 once during each revolution of the shaft 4. Simultaneouslywith the transmission of the train of waves, the condenser I1 is chargedfrom the source The condenser is discharged through the particularsegment 22 with which the brush 2| is in contact when the reflected waveor train of waves is impressed upon the microphone l8. The device 23corresponding to the particular segment is illuminated. Since thebrush-2| is rotated at a constant speedand all of the segments 22 are'of equal arcuate length, the particular device illuminated indicatesthe time elapsinghetween transmission of the wave and the reception ofthe reflected wave or the gistance between the system and reflectingsurace. dicatedby the illumination of a particular device.

The limit of distance which may be ascertained. however, cannot ofnecessity exceed the distance traversed by-the, train of waves in themolecular medium through which the waves pass to a reflecting surfaceand return to the transmitter in 4 to revolve one complete revolution.Frequently, as in an airplane, the pilot requires knowledge of the exactIn this manner the altitude or depth is in-' 10 to 100 feet theapproximate altitude is all that is desired. For determining thealtitude from one to'tenfeet the shaft 4 is rotated by gear 3 so thateach of the illuminating devices 23 indicates the altitude in units ofone'foot for an altitude of'from one to ten feet. The segments ber offeet indicated by the devices .23 associated with these segments when incontact with the brush 2| upon discharge of the condenser II.

IA to IOA to indicate the num- The number IA in the center of thesegment 22 corresponds to an altitude of onefoot, 2A to two feet and. WAto ten feet. For indicating the number of feet altitude from ten to onehundred feet in ten feet units-apparatus identical to that heretoforedescribed is employed.

When the altitude or depth exceeds ten feet the transmitter I4 andmicrophone I8 shift from the system forindicating from one to ten feetheretofore described to that for measuring ten to one hundred feet. Theshifting from the low range indicator to the high range indicator isaccomplished by the discharge of the condenser I'I through a relay 38.The condenser I1 is discharged through the relay 38 by the engagement ofa pair of contacts 35. A cam 34 having an elevation on the peripherythereof and fixedly attached to the shaft 4 controls the pair ofcontacts so that. once during each revolution of the shaft 4 thecontacts 35 momentarily are closed. The cam 34 is arranged on the shaft4 to control the contacts 35 so that these contacts engage -just priorto the transmission of waves by the transmitter I4 and after the brush2| has completely swept all of the commutator segments 22 numbered IA toI8A. Accordingly, if the discharge of the condenser I1 is not impressedacross one of the devices '23 through the segments 22 in one completerevolution of the shaft 4, it is discharged through an armature 31 and abreak contact 38 of relay 9 and contacts 35 to energize relay 38.

The armature of relay 38 is connected to ,ground, while the make contactis connected to the armature of a relay 4|. The relay 4| has twowindings, a small winding 39 and alarge winding 48. The passage ofcurrent through the small winding 39 is insufiicient to actuate thearmature of relay 4|, but when that armature engages its make contactthe energization of winding 39' is suflicient to maintain the engagementof the make contact and armature of relay 4|. The break contact of relay4| is connected to one lead of the winding 48 and one lead of the relay9. The other lead of the relay 9 is connected to the winding 39 and themake contact of relay 4|, while the other lead of the winding 48 isconnected to the make contact of a grounded armature 42 associated withthe relay 9. Current is supplied to relays 9 and 4| by a source ofcurrent 45 grounded at one terminal and connected at the other terminalto the winding 39. The momentary engagement of the armature and makecontact of relay 38 causes current to flow from ground, the source 45,the small winding 39, relay 9, the armature and break contact of relay4|, armature and make contact of relay 38 to ground. The momentaryoperation of relay 38 insures against a short circuit around the winding48 when the relay 9 operates. The passage of current through the smallwinding 39 is insufficient to actuate the armature of relay 4|. Thepassage of current through relay 9 causes the engagement of all thearmatures and make contacts of that relay including the groundedarmature .42 with its make contact. As a result of the engagement of thearmature 42 with its make contact, current is supplied from the source45 through'the small winding 39, relay 9 and large winding 48. Theenergizationof large winding- 48 causes the locking of the-make contactand armature 42- of relay 9 and the actuation and lockingcf the armatureand make contact of relay 4| In operating the relay' 4| as above setforth, the relay 38 is momentarily operated by the cam member 34. Themomentary operation of the relay 38 completes a circuit from the battery45 for operating the relay 9. After release of the the energizingcircuit has been opened. This applies to the relay 9 in providing delayin the opening of the relay contacts.

The circuit including relays 9, 38 and 4| is such that the firstactuation of relay 38 causes relay 9 to be energized and remainenergized until another impulse of current passes through relay 38. Asecond impulse for operating the relay 38 may come from the condenser II through the ring I28, brush I2| and segment I24 when the depth is lessthan 10 feet. Upon passage of the second impulse through relay 38, therelays 9 and 4| are deenergized. Upon passage of the second im-,

pulse through the relay 38 a ground is momentarily placed on itscontact. This condition causesa short circuit of the winding of relay 9in series with the winding 48 of relay 4|- which causes relay 9 toquickly release. This operation also causes relay 4| to release sinceits winding 48 is shorted in series with the winding of relay 9. Afterthe second impulse is received the relay 9 remains deenergized untilanother impulse passes through relay 38 when relay 9 is again actuatedand locked. This cycle of operation continues to shift alternately, inresponse to an impulse through the relay 38, the transmitter, condenserI1 and microphone from one range of distances to that of another.

I The engagement of armatures 8 and 3| of relay 9 to their respectivelyassociated make contacts 43, and 44 results in the shifting from one setof illuminating devices 23 with their associated segments, slip ringsand brushes to an identical set of illuminating devices |23 with theirassociated segments, slip rings. brushes and other apparatus capable ofindicating the particular distance within another range of distances. Ashaft I 84 of the apparatus for indicating a second range of distancesis driven by the motor I through the set of gears 2 and a set of gearsI83. The set of gears I83 is such that the shaft I84 revolves at a speedin a-manner similar to that of shaft 4 to indicate a particular distancewithin the second range. For example, the second apparatus may indicatedistances from ten to one hundred feet. If the first range indicatesfrom one to ten feet, shaft 4 revolves at ten times the speed of theshaft I84. The make contact 43 is connected to a pair of contacts I86similar to the contacts 6 to transmit waves once during each revolutionof the shaft I84. Contact 44 is connected to slip ring I28 to impressthe surge resulting from the discharge of condenser I I on one of aplurality of segments I22. The plurality of segments I22, a plurality ofilluminating devices I23, a slip ring I28,-and a brush I32 are identicaland perform the same functions respectively as segments 22, illuminatingdevices 23, slip ring 28 and brush 32. A slip ring I33 is employed whichserves the same function as the slip ring '33. A segment I24 is locatedin the sweep of the brush |2| so that brush I2I makes contact with thesegment I24 if the distance is less than w is required the transmitterand microphone are 4 the minimum indicated by the devices I23. SegmentI23 is'connected to relay 33 and when a. surge from condenser I1 isimpressed on that segment, relay "33 is energized. Accordingly, when thealtitude ordepth from the system is less than the indicated by thedevices I23, relay 33 is actuated. A portion of the slip ring I33 isbroken or insulates so that a circuit for the energization of relay 33is not completed when the brush' I132 engages the segment I23 Theenergization of relay 33 causes the engized to disengage the armatureand make contact of that relay with its make contact. The deenergizationof relay 3 causes 'armatures'3, 31 and 3| to engage with theirrespectively associated break contacts I, 35 and 33 to shift the systemto indicate the low range of altitude or depth by the devices 23. whenthe depth or altitude exceeds the maximum indicated by the devices 23,the relay 3 is energized to shift the indication to devices I23 in themanner heretofore described. Fig.-1A shows an indicating board 31 uponwhich the devices 23 and I234are mounted. The devices 23 may be arrangedin a circular pattern, with a number corresponding to the number of feetindicated'by each device immediately adjacent to that device. Thedevices I23 are arranged in a similar manner with a number correspondingto the altitude or depth in feet indicated by each device. In theembodiment illus trated the devices 23 indicate therange from one to tenfeet, while devices I23'indicate a range from ten to one hundred feet.Device 23 immediately adjacent to No. 1, Fig. 1A, is illuminated whenthe surge from condenser I1 is impressed upon segment 22 labeled IA. Inlike manner the devices 23 adjacent the numbers 2 to I3 are illuminatedwhen the condenser I1 is discharged through segments 22 marked 2A to I3A, respectively. Devices I23 adjacent to the numerals iii to I33 areilluminated when the brush I2I is in contact with the segments I22marked I3B to I333, respectively, at the moment of the discharge 'of thecondenser H. Y

The transmitter I3 and microphone I3 are located at a point the distancefrom a reflecting surface to which it is desired to be estimated. Ifthealtitude'of an airplane above the terrain placed on the underside of.the airplane. The transmitter and microphone are located from eachother at not greater than twice the minimum distance to be indicated ifshielding is not employed. Once during each revolution of the shaft 3 a.wave or train of waves is transmitted from the transmitter I3. At themoment of' transmission the condenser I I is charged. The condenser --IIis discharged in response to the reception of the reflected wave ortrain of waves by the microphone I3. The surge resulting from the Idischarge of the condenser-is impressed upon one r of the plurality ofsegments 22 to discharge the device 23 associated with that segment.Since the condenser breakdown of the tube I the brush 2| is rotated at aconstant speed the particular device illuminated indicates the timeelapsing between the transmission and reception of the reflected wave,or they distance between the-transmitter and the reflecting surface. If.for example, the brush 2i is in contact with the segment 22 marked 5A,the device 23 adjacent to the numeral 5 in Fig. 1A is illuminated. Ifthe distance between the transmitter I3 and reflecting surface isgreater than ten feet. the condenser is discharged by the engagement ofthe contacts 35 to energize why. The energizagtion ofrelay 33 causes theenergization of relay "3 to'shift the indication from devices 23 todevices I23 and to transmit a wave or train of waves once during eachrevolution of the shaft I 33.

A sonic or supersonic wave is then transmitted by the transihitter I3. 3Afterreflection on the terrain the wave or train of waves is impressedupon the microphone I3. The discharge of the condenser I! in response tothe reflected waves is impressed upon one of the segments I22. If, forexample, the distance of the plane be twenty feet above theterraim'thesegment "2 marked 23B is in contact with the brush I 2I at the time ofdischarge of the condenser I'I. When the reflected waves are impressedupon the microphone I3, the surge from the condenser I'I illuminatesdevice I23 adjacent to the numeral 23 in Fig. 1A. Device I23 adjacent tothe numeral 23 remains illuminated until it is de-ignited by therotation of the scavenger brush I32. If the plane drops to less than tenfeet, for example, eight, feet,

ment I23 to energize relay 33. The energization of relay 33 shiftstheindication to devices 23.-

A wave or train of waves is then transmitted once during each revolutionof the shaft 3. Upon Fig. 2 is a schematic diagram of an altimeteraccordance with thisinvention in which the altitude above the terrain isascertained by the illumination of one or more of a plurality ofdischarge devices. A low frequency oscillator comprising a gaseous spacedischarge device 53 having a self-biasing resistance to ailfordsufficient bias to sustain oscillations and a relay 5| in the outputenergizes the relay 5i at predetermined intervals. In the operation ofthe oscillator by the gas-filled tube 53 assume that the condenser isdischarged and that the tube 53 is not ignited. The condenser beinguncharged ofl'ers little opposition to the battery potential so that thetube 53 is quickly broken down. Upon 53 the condenser is charged andwhen the charge on the condenser reaches a predetermined point theopposition to battery potential is suflicient to insure the de-ignitingof the tube 53. The condenser then discharges through the coil of therelay 5| to effect momentaryoperation of the relay 5|. The above cycleof operations is then'repeated. The grid resistance determines theoperating points. The engagement of the make contact and armature ofrelay 5| causesthe momentary energization of two relays 52 and 53. Theengagement ofan armature 53 and a make contact associated with relay 53produces a wave or train of .waves in.

I1 is discharged through the scg- 1 53 results in the energization of arelay 55 supplied with current through the small winding of a relay 51by the source 58. The engagement of an armature and make contact 59 ofrelay 55 causes the energization of a large winding of the relay 51 todisengage the armature and break contact of that relay. In the operationof the relay 51 as aboveset forth, the relay 53 is momentarily operatedto effect operation of the relay 55. The relay 53 then releases andbefore release of the armature of the relay 55 takes place, the relay 51is operated, The operation ofthe relay 51 locks relays 55 and 51 inoperative position. When the energizing circuit of relay '55 is brokenby release of relay 53, there 1 will be a small delay before opening ofthe contacts 55 can take place. This-delay is sufiicient to insure theoperation of the relay 51. The pasrelay 51 while insufficient to actuatethe armature of that relay is capable of maintaining the ,armature inthe energized position. The relay 58 operates only momentarily and opensthe .contact 55 before the relay 55 is locked. An armature 55 associatedwith the relay 55 engages a make contact to charge a condenser 5| from a.scurce 52 through a resistance 53. The condenser continues to chargeuntil the relay 55 is de'energized.

A microphone l5 similar to that shown in Fig. 1 is employed for thereception of waves reflected from a terrain which are transmitted by thetransmitter I. The waves are amplified by an amplifier shown in theblock diagram in the, drawings. The amplified waves pass successivelythrough a transformer 10 and a copper-oxide .rectifier bridge 55 and theresulting unidirectional current is employed to energize a relay 55. Theenergization of relay 55 by the engagement or its armature and makecontact results in the kdeenergization of relay 55 by effectivelyremoving the source 58. The disengagement of armature 55 with its makecontact causes the removal of the source of current 58 from bothwindings of the relay 51. The disengagement of the arma- .surgeresulting from the discharge is impressedture 55 with its make contactremoves the source of charging current 52 from the condenser 5| and theengagement of the break ontact of armature 55 dischargesthe condenserthrough a copper-oxide rectifier 55 and a. resistance 15. The

upon' a lurality of gaseous space discharge devices 51 of the neon type.Each of thme devices 51 -has a different flash-over voltage. To obtainthe proper bias for securing the different flashover voltages for eachdevice a potential divider 55 is bridged across a source of current 59.Each of the devices 51 is connected to different points on the potentialdivider'to provide the required bias.- Since thecharge on the condenseris dependent upon the time between the transmission of a wave or trainof waves from the trans mitter I5 and its reception afterreflection onthe terrain by the microphone l8 and since this time is directlycorrelated with the distance between thetransmitter and the reflectingsurface, the devices 51 may be calibrated to indicate any particulardistance by means of varying their flashsage of current through thesmall winding of relay 55 which deenergizes relay 55.

microphone are in close proximity to each other the circuit between thecopper-oxide rectifier bridge 54 and the relay 55 is broken by theoperation of relay '52 simultaneously with the transmission of a wave ortrain of waves by the transmitter M.

The characteristics of the devices 51 are such that they remainilluminated at a much lower potential than that required to initiallyignite them. Accordingly, the devices 51 remain ignited even after thecharge on the condenser 5| has leaked off. The operation of relay 53causes the engagement of an armature 1| and a make contact of that relayto reduce the potential across these devices to substantially zerowhereby any device that. has been illuminated is de-ignited. Theengagement of another armature" and a make contact results in theremoval of any charge on condenser 5| through a resistance 13 when relay53 is operated.

The operation of armature 12 of relay 53 and the armature 50 of relay 55are such that any charge on condenser 5| is removed before thecommencement of the charging of condenser 5| from the source 52 andarmature 12 has disengaged from its make contact before the: armature 55has engaged its make contact.

In Fi 2A the devices 51 are shown mounted on a board 15. Alongside thecolumn of devices 51 is a scale 11. On this scale are numeralsrepresenting the calibrated distances indicated by each of the lamps.

The transmitter I4 and microphone l8 are located in close proximity toeach other on the underside of an airplane. The oscillator comprisingthe gaseous space discharge device 50 operates therelay 5| at periodicintervals. For example, the oscillation may generate a pulse once persecond to ten times per second depending upon the range of distances tobe determined. Relay 53 operatesto transmit a wave or train of wavesfrom the transmitter Hi and to commence to charge the condenser 5| fromthe source '52. The reflected wave or waves are impressed upon themicrophone ill to operate Condenser 5| is discharged through theplurality of discharge devices 51. Sincethe devices 51 flash over atdifferent voltages some are illuminated, while others are unaffecteddepending upon the charge accumulated by the condenser 5|. Since themagnitude of thecharge is directly correlated with the time betweentransmission of a wave or train of waves and the reception afterreflection on the terrain and since this tlmeis dependent upon thedistance between the system and the reflecting surface, the number ofdevices 51 illuminated indicates the distance between the system and thereflecting surface. The devices 51 are preferably arranged in a columnwith a calibrated scale index 11 arrangedalongside the column as shownin Fig. 2A. For example, if the distance between the system and thereflecting surface be fifty feet, the devices 51 immediately adjacent tothe numerals I0, 25, 35, 40. and 50 on the plate 12 of Fig. 2A becomeilluminated. After a predetermined period elapses the relay 5| againbecomes energized to transmit .another wave or train of waves.Simultaneously with the transmission of the wave or train of waves, anycharge on the condenser 5| is removed by the engagement of make contactand armature 12 and the lamps are -de-- ignited by the engagement ofarmature 1| with its make contact. Immediately following the removal ofany charge on the condenser 6! by the actuation of armature l2,condenser 3! commences to charge. The actuation of the discharge of thecondenser by the direct transmission of the wave or train of waves fromthe transmitter !4 to the microphone I3 is prevented'bhflisconnecting-the circuit from the rectifier bridge 64 to relay 65by the operation of relay 52. The wave or train of waves afterreflection on the terrain-againdischarges the condenser through theplurality of illuminating devices 61. The number of devices illuminatedindicates the distance between the system and the reflecting surface.This cycle of operations is continued to render constantly an indicationof altitude oidepth.

Figs. 3, 3A and 3B show a system in which distance is indicated in threedigits of a particular unit of measurement. If the unit of measurementbe feet, the system shown in Figs. 3, 3A

and 3B is capable of measuring the exact altitude or depth in feet from1 to 1000 feet. A

wave or train of waves is transmitted at predetermined intervals.Simultaneously with the transmission of the wave or train of waves acondenser is charged. The condenser is discharged upon the reception ofthe reflected wave or waves through one of. each of three sets ofilluminating devices. Each set represents a digit. The particulardevices illuminated depend upon the distance between the system and thereflecting surface. I

A constant speed motor 20! rotates a shaft. 204 by means of a set ofgears 203. Fixedly attached to the-shaft 204 is a brush 22!. A slipring- 220 is constantly in contact with the brush 22! and the brush isin engageable relation with ten commutator segments 222 having equalarcuate lengths so that at all times the brush is in contact with one ofthe segments or a segment 83. Each of the segments 222 is connectedtoone I electrode of a gaseous discharge illuminating device 223. Theother electrode of each device is connected through a limitingresistance 226 to one terminal of a source'of current 221. The otherterminal of the source 22'! is connected to ground through a resistance80. The electrodes of the devices 223 connected to the segwaves DZLSSES.

Another shaft 304 driven by the shaft 204 through a set of gears 303rotates one complete revolution in the time required for a. wave or.

train of waves to travel- 100 .feetto a reflecting surface and return tothe source. Another shaft 4041s driven by the shaft 304 through asystemof gears 403 so that the shaft 404 rotates one complete revolution inthe time'required for a wave or train of waves to travel ten feet to areflecting surface and return-to the source. A

- brush 32! and a brush! are fixedly attached to the'shafts 304 and 404,respectively.- brush 32! and the brush 42! are in constant contact,respectively, with aslip ring 320 and a slip ring 420. A plurality ofcbmmutator seg-' ments 322 of equal arcuate length are in engageablerelation with the brush 32! so that at all times the brush is in contactwith one of The the segments. Likewise, thebrush 42! is in engageablerelation with a plurality of segments .422 of equal arcuate length andarranged so that the brush' is in contact stall times with one of thesegments. Each of the plurality of comma-I tator segments 322 and '422is connected to one electrode of a plurality of gaseous space dis-.charge devices 323-and 423, respectively. The other electrodes ofdevices 323 and 423 anaconnected to one terminal of the source 221through resistances 323 and 423, respectively. The electrodes of thedevices 323 and 423 commend to the commutator segments are-alsoconnected through resistances 323 and 423,'respectively, to ground.-'Each of the slip-rings 223. 323 and 420 is connected through acopper-oxide rectifier 82 to the make contact of a relay 3!. The.devices 223 indicate the depth or altitude in feet in 100 units, thedevices'323 in feet in units of ten and devices 423 in single units. Thesegments. 222 are marked !C to 36 to correspond Likewise segments 323are indicated 3D to 3D to correspond respectively to altitudes in stepof ten feet from 0 to feet and the segments II to SE to correspondrespectively from 0 to ii feet.

The segment 83 and a grounded segment 34 are in engageable relation withthe brush 22! at the beginning of rotation of that b I ments 83 and 34are arranged in re ation to the sweep of the brush 22! so that the brush22! engages these contacts'when the slip rings 323 and .420 are engaged,respectively, with segments 322 and 422 connected to devices 323 and423, respectively, which corresponds to zero indication and the brush22! is between the segments 222 marked 90 and IC. The engagement ofthesegments 33 and 04 by the brush 22! results in the emissionof a wave ortrain ofwavesby a transmitter '!4 to an altitude of from to 900 feet,ly, with which these segments are associated.

by means of the energization oi .an inductorl alternator !3 through arelay 33 from a source of current 85; The transmitter l4 andthe-inductor-alternator !3 are similar to those employed in the systemshown in Fig. 1. The passage 02 current through relay 03 results-in theiengagement of an armature and make contact 33 associated with thatrelay. to charge a condenser 32' from a source 3! through a resistance32. "After the wave or train of waves is reflected upon the terrain, thewave or train of waves is impressed upon a microphone 13. The impressedwaves cause a unidirectional current to flow in the output of anamplifier which is connected to the microphone i3. This unidirectionaleurrentoperates a relay 0! through a break contact and armature 91 ofrelay as. The en agement of s make contact and an armature 33- ofrelayll'- actuates a relay 3'! supplied with current by a source 89. Oneterminal of the condenser is connected to the armature ofrelay 3!. --Theengagement of the armature and make-contact of relay 3! causes thecondenser to through the slip rings .220, 323 andf423 and an particularcommutator segment upon which-the brushes 22!, 32! and 42! are'e'nsagedat thetime.

of discharge through the particular devices 223. 323 and 423 connectedto these-e segments. The particular devices 223, 323 and 423 remainilluminated until just prior to the The devices 223, 323 and 423 havesimilar-char acteristics to device 23 employed in Fig. 1." M

cordingly, once the devices are main illuminated at a lower terminalthan that required to initially ignitethem. Howupon the segments 223,323 and 423 until the contact and armature 94 have opened. In the aboveoperation a delay is caused in the discharge of the condenser 93 withrespect to the closing and opening of the contacts 94 by the build-uptime in the energizing circuit of the relay 8| under control of thecontact members 88. A further delay in discharging the condenser 93 isprovided by the time travel of the armature for the relay 8|. The aboveperiods of delay are sufflcient to insure that the condenser 93 does notdischarge .until after the contacts 94 have closed and opened.Accordingly, the previous altitude reading is not removed until justprior to the next reading. To prevent an indication 'as a result of thedirect transmission of waves or trains of waves from the transmitter |4tothe microphone |8 the circuit from the amplifier to the relay 81 isbroken at the moment of transmission by the disengagement of the breakcontact and armature 91 associated with relay 88.

A suitable device for housing the indicating devices 223, 323 and 423 isshown in Figs. 3A and 3B.- A board 95 having three sets of digits from 1to 9 is employed as a panel on a housing 98. Each of the numerals istranslucent or transparent, the remainder of the panel 95 being opaque.The illuminating devices 223, 323 and 423 are placed, each set ofdevices in a single row, in light-proof compartments in the housing 98immediately behind the numbers and digits to which they correspond.

A wave or train of waves is transmitted by the transmitter 14 as aresult of the engagement of the segments 84 and 83 with the brush 22|.This engagement occurs once during each revolution of the shaft 284.Simultaneouly, with the transmission of the wave or train of waves thecondenser 93 is charged. After reflection on a surface the wave or trainof waves is impressed upon the microphone l8 to operate relay 81. Theope:- ation of relay 81 in turn actuates relay 8| to discharge thecondenser 93 through the slip rings 228, 328 and 420. The discharge isimpressed upon the particular segments 222', 322 and 422 with which thebrushes 22|, 32| and 42| are at the time of discharge. engaged. Thesurge passes to the particular gaseous discharge devices 223, 323 and423 to which the particular segments are connected. These particulardevices 223, 323 and 423 are ignited. The translucent or transparentnumerals on the panel with which these devices are associated becomeilluminated. The characteristic of the devices 223, 323 and 423 is suchthat once broken down they remain illuminated at a lower terminalpotential than that initially required to ignite them. The potentialfuror train of waves. Simultaneously with the transmission of the waveor train of waves the condenser 93 is charged. After the wave or trainof waves is reflected from a surface it is impressed upon the microphonel8. Relay 81 is, as a result,

actuated. Any of the devices 223, 323 and 423 which were ignited as aresult of the reception of the previous wave or train of waves arede-ignited by the engagement of the armature and make contact 94associated with the relay 81. Condenser 93 is discharged through thedevices 223, 323 and 423 which are connected to the particular segments222, 322' and 422, respectively, with which the brushes 22 32| and 42|are at the time of dischargeengaged. The armatures and contacts ofrelays 81 and 8| are such that the devices previously illuminated arede-ignited immediately prior to the discharge of the condenser 93through the commutator segments 222, 322. and 422. This cycle ofoperations is continued to indicate continually the altitude or depthbetween the systemand the reflecting surface.

While these systems have been described for use in the determination ofaltitude or depth from a point to a reflecting surface, they are equallyadapted toascertain distance between two points. For this purpose, thetransmitter I4 is placed at one point and the microphone I8 is locatedat the other point. Radio or telegraphic communication between the twopoints affords means for relaying the time of reception of thetransmitted sonic or supersonic wave by the microphone l8.

Although the distance determining systems are described for use onairplanes, they are similarly applicable to ships for depthdeterminations at sea.

While preferred embodiments of this invention have been illustrated anddescribed, various modifications therein may be made without departingfrom the scope of theappended claims.

What is claimed is:

1, In combination, a source of longitudinal waves, means fortransmitting a wave from said source at predetermined intervals, 9.plurality'of gaseous space discharge devices, means responsive to saidwave upon receipt after reflection for selectively igniting one of saiddevices to indicate distance, means controlled by said responsive meansfor maintaining the selected indication between signals, and means forextinguishing the selected device prior to the next selection of one ofsaid devices.

2. In combination, transmitting means for emitting a wave, control meansfor operating said transmitting means, a condenser, means operated bysaid control means for commencing the charging of said condenser toeffect a steadily increasing strength of charge on the condenser, meansresponsive to said wave after passage through a molecular medium todischarge said condenser, and means-responsive to the magnitude of theelectromotive force produced by the discharge of said condenser toindicate distance.

3. In a system for indicating distance, means for indicating a firstrange of distance, a second indicating means for .indicating a secondrange of distances, means for normally maintaining said first rangeindicating means in condition to be responsive to a signal indicating adistance-in said first range'and said second range indicating means inunresponsive condition, and means responsive to a reflection indicatinga certain distance in said second range for rendering responsive saidsecond indicating means. 4. In a system for ascertaining distance, afirst indicating means for indicating a first range of distances, -asecond indicating means for indicating a second range of distances,means responsive to an indication of a certain distance in said secondrange for rendering responsive said second indicating means and fordisabling simultaneously said first indicating means.

5. In a system for indicating distance, a plurality of indicating meansfor indicating a range of distances, each of said means indicating adiiferent range of distance, and means, responsive to an indication of adistance within one of said ranges, for rendering responsive one of saidindicating means and .disabling all other indicating means.

' 6. In a system for the determination of distance, a first indicatingmeans responsive to longitudinal waves for indicating a first range ofdistances, a second indicating means normally unresponsive tolongigtudinal Waves for indicating a second range of distances, andswitching means, responsive to an indication within said. second range,for rendering said second indicating means responsive to longitudinalwaves and for disabling said first indicating means.

7. In combination, a first plurality of gaseous space discharge devicesfor. indicating a range of distances, a second plurality of gaseousspace discharge devices for indicating a second range of distances,means, responsive to said Waves within said first range of distancesafter passage through a molecular medium, for igniting one of saiddevices of said first plurality of devices to indicate distance, means,responsive to waves within said second range of distances, for renderingresponsive said second plurality of devices and for renderingunresponsive said first plurality of devices to longitudinal waves.

8. A system for the determination of distances, comprising means fortransmitting a longitudinal wave, control means for operating saidtransmitting means at predetermined intervals, a source of current,storing means for storing said current, means responsive to'said controlmeans for commencing to store said current by said storing means,receptive means for receiving said wave after passage through amolecular medium, means for preventing the actuation of said receptivemeans by the direct emission of said longitudinal wave, a plurality ofgaseous space discharge devices, each of said devices biased to adifferent flash-over voltage, a scale associated with said plurality ofdevices, release means, responsive to the reception of said wave by saidreceptive means, for releasing stored energy accumulated by said storingmeans, and means for impressing the released energy on said plurality ofdevices whereby an indication of distance is obtained by observing theillumination of said devices on said scale.

9. A system for the determination of distance,"

comprisingmeans for transmitting a longitudinal wave, control means foroperating said transmitting means at predetermined intervals, meansactuated by said control means for charging a capacitance, a commutatorcomprising a plurality .of segments, gaseous space discharge devicesrespectively associated-with said segments, receptive means forreceiving said wave after reflection on a surface, receiving meansresponsive to'the reception of the reflected wave by said receptivemeans for discharging said condenser, means actuated by said controlmeans for preventing the actuation of said receiving means by the directemission of said wave, a brush in engageable relation with and rotatableat a constant speed over said plurality of segments for impressing thepotential resulting from the discharge of said condenser on one of saiddevices, and means for denext operation means for extinguishing anyselected device priorv to the next selective operation.

11. In a system for indicating distance, transmitting means for emittingsignal waves, control means for operating said transmitting-means atpredetermined intervals, a plurality of gaseous space discharge devices,a capacitance, means responsive to said control means for commencing thecharging of said capacitance to efl'ect a steadily increasing strengthof charge on the capacitance, means responsive to reflected signal wavesfor discharging said capacitance, means for igniting said devices innumber according to the magnitude of the electromotive force produced bythe discharge of said capacitance to indicate cation between signals andmeans for extinguishing any selected device prior to the next selectionof any of said devices.

12 In a system for indicating distance, transmitting means for emittingsignal waves, control means for'operating said transmitting means atpredetermined intervals, a plurality of gaseous space discharge devices,means responsive toa refiectedsignal wave for igniting at least one ofsaid plurality of devices to indicate distance, means for maintainingsaid device ignited between signals, and means governed by said controlmeans for extinguishing anyselected device prior to the next distanceindication.

13. In a system for determination of distance, transmitting means foremitting signal waves, control means for operating said transmittingmeans at predetermined intervals, a pluralityoi' gaseous space dischargedevices, a capacitance, means responsive to said control means forcharging said capacitance, means responsive to reflected signal wavesfor discharging said capacitance, means for igniting at least one 01'said plurality of devices by the discharge from said capacitance .toindicate distance, means controlled by said means responsive to thereflected wave for maintaining the selected indication between signals,and means controlled by the reflected signal waves for extinguishing anyselected device an interval before the next distance indication.

14. In a system for indicating distance, trans:

35 distance, means for maintaining the selected indii discharging saidcondenser, auxiliary means for igniting at least one of said pluralityof devices by the discharge from said condenser to indicate distance,and means governed by said auxiliary means for extinguishing said deviceprior to the .next distance indication.

'15. In combination, a capacitance, transmitting .means for emitting alongitudinal wave, control means for operating said transmitting meansat predetermined intervals, means operated by said control means forcharging said capacitance,

means responsive to said wave for discharging said capacitance, 'aplurality of gaseous spacedischarge devices, means responsive to thedischarge of said capacitance .for selectively igniting at least one ofsaid devices to indicate distance, means for maintaining the selectedindication between signals and means for extinguishing any selecteddevice prior to the next selective operation.

ARNOLD B. BAILEY.

